This invention relates to fuel injection devices for internal combustion engines, and more particularly to a fuel injection device for diesel engines which electronically controls fuel injection flow rate of a distribution-type fuel injection pump.
In a conventional fuel injection pump of the type described, fuel fed to a low pressure chamber by a feed pump is applied with high pressure by a plunger, with the fuel under high pressure supplied to respective cylinders. The fuel injection flow rate is adjusted such that an ending time is determined by a centrifugal governor, at this pump-feed ending time, the fuel is returned to the low pressure chamber through a spill port for adjustment. More specifically, the centrifugal governor comprises a governor shaft rotatable in accordance with engine rotational speed, a fly weight secured to this shaft, a tension lever connected through a spring to an accelerator lever, a spill ring for controlling opening and closing of the spill port of a plunger and a support lever connected to the spill ring (for moving the spill ring on the plunger in accordance with the engine rotational speed and a rotational angle of the accelerator lever). The centrifugal governor is adapted to determine a position of the spill ring in accordance with the movement of the fly weight, the tension lever and other levers to thereby determine the fuel pump-feed ending.
However, the velocity of movement of the plunger in the axial direction is in accordance with the engine rotational speed, and therefore, even if the position of the spill ring is made constant, the injection flow rate per stroke is varied as the velocity of movement of the plunger becomes high. Furthermore, with the conventional fuel injection flow rate control as described above, in order to change the injection flow rate in accordance with the engine rotational speed, i.e., to change the torque characteristics of the engine, it is necessary to use the very complicated mechanism as described above. Furthermore, it is difficult to desirably design the torque characteristics.